1. Field of the Invention
The present invention is directed to an apparatus for transferring flowable material, particularly bulk material, and more particularly to an apparatus of the type usually referred to as an Intermediate Bulk Container or IBC.
Such an apparatus usually comprises a container for receiving material which includes at least one opening for discharging said material, and optionally another opening for charging the container. In addition containers are known which have a plurality of discharge openings. For the discharge opening, there is a closure member which is displaceable from an open position to a closed position. An actuator displaces the closure member from the open position to the closed position, or vice-versa, along an axis of actuation.
There is at least one docking surface for engaging a counter-surface of a take over device, formed by another container, a hopper or the like. This counter-surface defines a charging opening of the take over device which is normally closed by a cover or lid. For removing the cover, a variety of devices were suggested in the past, but one of them uses a source of vacuum, and at least one vacuum operated lid removal device, a surface of which engages the cover or lid and opens the charging opening of the take over device. For this engagement, the lid removal surface is connected to the vacuum source via a corresponding suction conduit.
2. Background Information
An apparatus of this type is disclosed in U.S. Pat. No. 5,351,864, which is hereby incorporated by reference. According to this patent a vacuum device replaces other known devices, such as a lid lifting magnet in accordance with DE-B-1 188 882 or a mechanical removing device according to EP-A-0 847 946, for example, the disclosures of which are hereby incorporated by reference. All these lid lifting or removing devices have in common that, although the cover or lid has to be removed automatically, assuming that they work reliably, there is nothing to ensure or monitor whether this is actually the case. In principle, it does not matter whether it is the question of a liquid material or of bulk material which forms a flowable material, although the latter will be the rule. The take over part, which may be closed by the cover, will normally be an IBC, as mentioned above, although it may simply be constituted by a filling opening of a charging hose, as disclosed in EP-A-0 384 826, which is hereby incorporated by reference.
For example three typical conditions can be envisaged where a vacuum device and its suction cup according to U.S. Pat. No. 5,351,864 will and must fail:
the suction cup is worn out and/or has a hole so that an underpressure necessary for lifting the cover cannot build up. This will occur regularly after a certain period of operation which depends on the abrasivity of the flowable material, the operational conditions and the working time.
the cover is soiled by bulk material or other flowable material so that the suction cup does not find a hold and, thus, does not lift the cover.
the cover is somewhat inclined and not in a position perpendicular to the axis of actuation.
All these inadequacies are partly due to the construction of the vacuum operated lifting device used heretofore. It is quite clear that it is the question of relative massive structures, which led one to assume that the suction cup had consequently also to be sturdy in order not to cause tilting the cover during reclosing due to too great a flexibility. Therefore, the suction cup was substantially formed as a bubble cap which had an enlargement surrounding a suction opening and passed over into a narrowing section, so that the cover should have no opportunity to tilt after sucking it on. However, the inventor""s discovered restricted flexibility and the possibility to move caused the above enumerated inadequacies.
Therefore, it is an object of the present invention to efficiently avoid the above-mentioned failures in operation.
According to the present invention, this object is achieved in an apparatus of the type described by providing means for ensuring an engagement of the lid removal device or surface with the cover. Exemplary embodiments include either forming the lid removal surface immediately on the closure member of the container and/or by providing a monitoring arrangement for monitoring the engagement of the lid removal surface and the cover, the monitoring arrangement emitting an engagement signal either when the lid removal surface engages the cover properly and/or optionally emitting another signal when this is not the case, the latter being preferred. This signal may be evaluated either by simple indication or alarm or by initiating a lid removal program anew for another trial.
The lid removal surface on the closure member can preferably be formed on a suction cup which, when seen in a direction from said suction opening to said vacuum connection opening, has at least one succession of a first narrowing section to form a pleat and a second, enlarging section. In this way, the former disadvantage of the cup being too stiff is avoided due to the pleat. The greater flexibility enables automatic compensation of any disengagement of the suction cup on the cover. On the other hand, for reasons of required space and limitation of flexibility, it is advantageous if the suction cup comprises three pleats in maximum or even only two narrowing sections in maximum.
It can be useful to form the closure member with a first, inner conical surface, which is known per se, but in the present context provides an increasing effect of the vacuum applied through the closure member itself when the cover is sucked in. In addition, the cover can comprise a second, outer conical surface for insertion into the first conical surface, and this outer conical surface is preferably complementary to the inner conical surface of the closure member. In such a case, the two conical surfaces may provide a sealing surface and a counter-sealing surface.
It is surprising that by the simple measure of forming the lid removal surface directly on the closure member itself a variety of advantages are achieved. For example,
by omitting the usual mechanism for displacing the lid removal surface in relation to the closure member, the design is simplified. It is only necessary that the cover is moved close enough to the closure member that the latter is enabled to suck the cover onto the lid removal surface;
in doing so, possible failures are reduced, and the former mechanism, since omitted, need not be maintained or repaired;
the whole structure is simplified so that its costs of manufacturing are reduced;
since the whole closure member is used for sucking the cover on, a much larger cross-section of the suction opening, which faces the cover, will result so that the position of the cover is better defined than with a limited, smaller cross-section, as disclosed in U.S. Pat. No. 5,351,864 where only a small difference of the cover""s position from the nominal one precisely perpendicular to the axis of actuation will result in a large angular deviation of the cover""s edges due to leverage;
in addition, the lid removal surface directly on the closure member will, in general, be larger than in the prior art, thus ensuring safe holding of the cover.
In addition or as an alternative, the above-mentioned monitoring arrangement may be provided for monitoring the engagement of the lid removal surface and the cover. Monitoring may be effected by a sensor, such as a sensor which determines directly the position of the cover relative to the closure member (for example an ultrasonic reflected wave sensor for determining the distance of the cover from an inner surface of the closure member) or an indirect acting sensor which determines the underpressure and or the flow rate building up between the cover and the closure member or in a suction line connected to the latter. As mentioned above, this monitoring arrangement will provide a signal to be evaluated which indicates whether the cover is engaged properly or not by the lid removal surface. A directly measuring position sensor would determine whether the cover, when being lifted by the lid removal surface, changes its relative position to the closure member, thus indicating that it is not held properly. However, the indirect method is much simpler and, therefore, preferred. Moreover, it is preferred to determine the pressure rather than the flow rate, because with pressure one of the above failures can reliably determined in a simple way. For example, at least one sensor arrangement can be coupled to a suction conduit, the sensor arrangement providing a positive (xe2x80x9clid is engagedxe2x80x9d) and/or a negative (xe2x80x9cengagement has failedxe2x80x9d) signal to the evaluation device.
As to the evaluation, various approaches can be used. For example, the signal of the monitoring arrangement can initiate a program which tries again to remove the cover (which may also be shifted horizontally after engagement instead of or in addition to being lifted), optionally after blowing dust or some bulk material away which can possibly be present on the cover and may prevent proper sucking and lifting it. This may either be done manually by switching an initiating switch on or by a docking or position sensor, as mentioned above, which releases such an initiating switch member (optionally formed by a switch valve).